A ball lens connector part of the kind mentioned above is known from European Patent Application No. 207,552. An optical fiber the core of which coincides substantially with the center line of the circumference of the tubular housing is connected in the tubular housing of the connector part described in the said Application. The end face of the end part of the fiber clamped in the housing extends perpendicularly to the fiber core, i.e. the normal of the said end face and the center line of the fiber core extend in parallel and hence enclose a mutual angle of 0.degree..
It has been found that the total reflection of light radiated in the fiber is still considerable in the known ball lens connector part. These total reflections are composed of reflections of light on the end of the optical fiber which is present just in front of the ball lens (end face reflections) and of reflections on the ball lens (ball lens reflections). The reflected light radiates via the fiber core in the direction of the light source used. In the case in which the light source used is a laser, the said reflections may give rise to undesired floatings in the frequency, phase and/or amplitude of the radiated laser light. In spite of the use of antireflex coatings known per se on the ball lens, as a result of which the ball lens reflections are reduced, it has been found that the total reflections in the known ball lens connector part are still unacceptably high.